1. Field of the Invention
This invention relates to liquid-propellant, expander-cycle rocket engines and especially to such engines which use a regenerative system for heating the oxidizer which drives the propellant turbines.
2. Description of the Prior Art
The evolution of rocket engines has led to a demand for and development of engines providing higher and higher output thrust. To develop higher thrust in rocket engines, higher pressure in the combustion chamber is required, since output thrust is directly related to chamber pressure and this, in turn, requires higher propellant flow rates.
Provision of propellants at higher flow rates has been accomplished in the past by gas-generator engines and by expander-cycle, heated fuel-drive engines. The simple gas-generator engine uses a portion of the fuel to generate gas to drive the propellant drive turbine and the turbine exhaust is directed into the expansion section of the nozzle. A second type of gas generator is the staged-combuston monopropellant gas generator. A third type is the staged-combustion, fuel- or oxidizer-rich preburner in which both fuel and oxidizer are burned. Gas generators are basically unsafe since they burn fuel, or fuel and oxidizer, and can generate high temperatures which can cause the engines to explode or burn up associated downstream turbines and components if they operate off design conditions. Gas-generating preburners also require a variety of associated equipment, such as high-pressure valves, controls, ignition systems, sensors, combustors and injectors, which adds weight, complexity, unreliability and cost to rocket engines.
The oxidizer expander-cycle engine described herein can be used to provide the heated gas necessary for driving the propellant turbine. This engine heats the oxidizer in the cooling jacket of the engine nozzle and utilizes the turbine exhaust gas to preheat the oxidizer in a heat exchanger, or regenerator, before the oxidizer is fed through the cooling jacket of the engine. The oxidizer expander-cycle engine has the high-performance potential of the fuel-rich or oxidizer-rich staged-combustion engine without the disadvantges of the gas-generator preburner engines. The present invention constitutes an improved expander-cycle engine using an oxidizer-driven turbine.